Dual fuel outboard motors are used in the far east for the most part. The motor is started and warmed up using gasoline and then transfered to kerosene. Only a small gas tank is required and it is typically located under the upper engine cover. It has to be vented. This has been done with a screw vent in the tank or cap which necessitates removal of the engine cover to open or close the vent. If the operator does not close the vent, gasoline can spill out when the motor is transported. That is a fire and explosion hazard. It is desirable to make the vent automatic to make the use of the engine simpler and to eliminate human error.
The prior art shows fuel couplings incorporating a valve which is opened by the coupling action to vent the tank being connected. See U.S. Pat. No. 4,269,219 and 4,040,456. These patents do not vent a tank different than the tank being connected.